J2108 Offset printing machine is not allowed to troubleshoot

After a few years of use, a J2108 offset press appeared misprinted. This phenomenon is good and bad. After many inspections, it has not been able to eliminate the problem.
Misregistration is generally divided into left and right inaccurate and inaccurate. The right and left overprinting of the machine is not accurate. In inspection and repair, we first check whether the drive pin is broken, whether the front specified axis is stable, and adjust the height of the front gauge. In the trial printing, we also adjusted the front and rear positions of the platen and the presser brush. The problem could not be solved. But the machine's paper feeding is stable, there is no paper skew phenomenon, and the paper feeding time is also suitable.
We also tried to use two-sided gauges respectively. As a result, overprinting was not allowed to be serious when using the side-slip gauges, and the other side gauge was not in place. At the same time, when checking the front and back position of the front gauge, it was found that the amount of paper pulled by one side was only 3mm, while the amount of paper pulled by the outer side was more than 4mm. This may be the problem. Because the current regulations are not flat, the edge of the paper roll is not parallel to the axis of the drum, so the phenomenon of not appearing in the printing does not appear.
We adjusted the position of the front gauge to make it 6mm. In this way, failure to overprint in printing is ruled out.